1. Field of the Invention
The present invention relates to a power conversion apparatus.
2. Description of Related Art
A general power conversion apparatus includes switching elements and a control circuit section for controlling the operation of the switching elements. IGBTs made of silicon semiconductor material are used as the switching elements, for example. The control circuit section causes the IGBTs to perform switching operation to perform electric power conversion.
There is a demand for reducing the loss of switching elements of a power conversion apparatus as described above. To address such a demand, it is proposed to use MOSFETs made of wide bandgap semiconductor material such as SiC or GaN instead of IGBTs made of silicon semiconductor material. The on-resistance of the IGBT is large in a small-current area because there is diffusion potential. On the other hand, the on-resistance of the MOSFET is small even in a small-current area because there is no diffusion potential. Accordingly, it is possible to reduce the loss of the power conversion apparatuses by using the MOSFET.
Also, it is proposed to use wide bandgap semiconductor material as material of a diode to be reverse parallel-connected to the MOSFET to reduce the recovery loss of the diode to thereby further reduce the entire loss of the power conversion apparatus.
However, the MOSFET or diode made of wide bandgap semiconductor material is expensive compared to the IGBT or diode made of silicon semiconductor material. Accordingly, the manufacturing cost of the power conversion apparatus increases considerably if all the elements thereof are made of wide bandgap semiconductor material.